This invention relates to strain relief of electrical conductors, and in particular to strain relief devices and strain relief bends in flexible electrical conductor strips.
Flexible conductor strips, commonly referred to as xe2x80x9cflex strips,xe2x80x9d are often used to electrically interconnect circuit boards in an assembly, connectors on a circuit board, and other electrical devices that move relative to one another either during test and assembly or during their functional life. Flex strips are generally well known in the art as multiple flat electrical conductors usually laid out in parallel strips and encased in a flexible nonconductive material, such as kapton, and having connection means, usually either pins or holes for insertion of male pins, at either end of each conductive strip. In use, the flex strips are mounted on the electrical assemblies or devices to be interconnected with solder joints at the ends of the conductive strips insuring electrical connectivity. The resulting flexible electrical interface, i.e., the flex strip, can be bent and twisted within limits and remains operational. However, if the flex strip is torn, creased or pressed into the wrong position, the thin conductive traces therein may be broken, destroying the signal path, thus causing loss of data. Further, if the flex strip is repeatedly stressed beyond certain limits, the fatigue life of the conductors may be exceeded causing the resistance in the conductor to increase, or even failure over a period of use. Replacing the flexible conductors is very difficult and time consuming once they are in place within a computer assembly, therefore it is important that the flex strip remain fully operational for use over many years, beyond the expected life of the machines in which they are placed.
The present invention provides a preset bend of a known curvature and orientation in a flexible conductor strip interconnecting first and second electrical contacts. The distance between the first and second electrical contacts varies as they are connected to and removed from each other. According to one aspect of the invention, the preset bend includes a substantially straight first leg extending substantially perpendicularly to an axis of relative motion between the first and second interconnected electrical contacts feeding into a substantially hemi-circular curve, which continues into a second leg extending toward the second electrical contacts in their spaced apart position.
The preset bend is formed in a flexible electrical conductor strip, such that the flexible conductor strip is formed with a substantially straight first leg extending substantially perpendicularly to an axis of relative motion between the first and second interconnected electrical contacts feeding into a substantially hemi-circular curve, which continues into a second leg extending toward the second electrical contacts in their spaced apart position.
According to yet another aspect of the invention, the invention provides a strain relief assembly having a first conductor guide defining a concave surface facing toward the contact mounting surface and away from the first spaced apart position occupied by the second electrical contacts in their spaced apart position, and a second conductor guide defining a convex surface facing toward, substantially coextensive with, and spaced a predetermined distance away from the assembly""s concave surface.
According to still another aspect of the invention, the invention provides an electrical connector that is translatable relative to a mounting surface between the first and second spaced apart positions, which are each spaced away from electrical contacts that are stationary relative to the mounting surface. The translatable electrical connector is substantially enclosed within the connector housing, which is fixed in a position relative to the mounting surface and the stationary electrical contacts. The connector housing also preferably includes at least one of a third conductor guide mounted on one side the mounting surface and extending therefrom toward the conductor guides. A fourth conductor guide mounted on the other side adjacent to the mounting surface and extending therefrom may also be used.
According to other aspects of the invention, the present invention provides various methods for forming a preset stress relief bend in a flexible electrical conductor strip.